Teamviewer, One of the best remote control application. It lets you remotely access and troubleshoot PCs over the Internet / LAN. Team Viewer provides easy, fast and secure remote access to Linux, Windows PCs, and Macs. Free for personal use but have to pay for commercial use, though you can use the trial version there.

There are two ways to install it, either in graphics mode or in terminal mode. Both are explained down here.

Ubuntu launched it's latest 12.04, named Precise Pangolin, yesterday with some new features and lots of performance improvements. The main thing which caught my attention is the LTS (Long Term Support) release, which surely will make it favorite of a lots of people, and this means that 12.04 will be officially supported for the next 5 years. On top of that it also provides new Linux desktop for LTS users, with support of non-linux applications like Vmware, Citrix etc.

You must have seen this error while installing some packages though apt-get or aptitude in Ubuntu. The reason for the error is the the GPG keys for that package is not available in your system DB, hence the package can't be verified.
The fix is pretty much simple, you just need to download the GPG keys for the package and then re-install the package.